Balancing inputs to the swashplate to equilise torsional loads on the blades

[blazkowic]

Hello, fellow rotorheads!
I've been going trough the syllabus for Aircraft general knowledge and stumbled upon a learning objective at Helicopter: Flight Controls and it goes like this:

"Describe the swashplate or azimuth star control system including the following:
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- balancing of pitch/roll/collective inputs to the swashplate to equilise torsional loads on the blades"

If someone could please explain what's up with this question or at least point me in the direction where I could find an explanation for it.

Thank you!

[GipsyMagpie]

I think this may clumsily be referring to the need to equally space the jacks round a swashplate instead of having the logical position of 2 left/right jacks and one fore/aft jack. The logocal position unevenly spaces the support to the plate...the penalty for evenly spacing the jacks is you need a mixing unit. Remember I'm not talking about left/right/fore/aft in relation to the fuselage - you have to place the jack ahead of where you want the action to occur on the blade due to the precessive effect generated on the head (phase lag - which is dependant on head type and the density altitude). The learning objective could also be referring to the balance between the distance of the pitch operating arm and swashplate lead able used to get the advance angle (90° in a teetering head).

Do a search for rotor advance angle and the Google books result (third down) has a pretty picture on page 140 which shows you what I mean.